Integrated deck structures are prefabricated decks designed to be installed as a unit onto a substructure at an offshore location. These substructures provide a framework for anchoring the deck, and are generally either fixed or floating. Fixed substructures are attached to the ocean floor, typically by means of a gravity base or piled foundations. Floating substructures are sufficiently buoyant such that their own weight is carried by the buoyancy, and position is maintained by an anchoring system.
When mating an integrated deck structure with a substructure, the deck is usually transported to the substructure by means of a barge. For most applications, a single barge is used; however, in mounting deck structures onto single leg substructures such as those used in arctic climates, multiple barges may be required. Typically, the barge is moved into position proximate the substructure and ballasted to lower the integrated deck structure onto the substructure and transfer its load thereto. Once the integrated deck is in place and the load transferred to the substructure, the barge is disengaged and taken back to shore.
Many complications can arise during this mating procedure, due in large part to the relative motion between the deck and the substructure caused by ocean waves, currents and wind. This movement can cause the deck and the substructure to collide, resulting in appreciable damage to the equipment and unwanted delays to repair or replace any equipment so damaged. This movement also complicates the alignment of the deck with the substructure, which is necessary to insure a proper mating between the two.
Prior art solutions to the alignment problem primarily involve stabbing a smaller diameter leg, either on the deck or the substructure, into a corresponding larger diameter collar on the other component. This collar directs the smaller diameter leg into alignment once the leg is within the collar. This solution is satisfactory only in the respect that it does not require initial perfect placement of the deck and the substructure for proper alignment; however, the wind and water forces can still cause the aforementioned damaging collisions.
Prior art solutions to the collision problem primarily involve the use of a damping (shock absorbing) and/or cushioning (deformable spring) means to lessen the impact of these collisions. These prior art systems, however, suffer from many shortcomings. First, these systems do not readily allow for control over of the amount of cushioning and damping during the mating procedure, that is, these parameters are constant during the mating operation. Also, the prior art systems tend to utilize complex hydraulic and mechanical devices as aligning, cushioning, and damping means, thus complicating the mating procedure and increasing the risk of operator error, machine failure, and resultant equipment damage. The present invention is aimed at overcoming these shortcomings in an economical fashion.